A dental ceramic can either be coloured by incorporating pigments into the ceramic material or using metal salts containing solutions which are to be applied on the surface of partially sintered dental ceramic with the aim to colour the dental ceramic in its entirety.
In this respect DE 196 19 168 A1 describes a ceramic colouring solution consisting essentially of water and a palladium containing compound dissolved therein. The solution might further contain co-solvents such as alcohols, glycols, glycol ether or polyethylene glycol.
WO 2004/110959 relates to a colouring solution for ceramic framework. The solution comprises a solvent (e.g. water), a metal salt and polyethylene glycol having a Mn in the range of 1.000 to 200.000.
WO 00/46168 A1 (corresponding to U.S. Pat. No. 6,709,694 B1) refers to colouring ceramics by way of ionic or complex-containing solutions containing defined concentrations of at least one salts or complexes of the rare earth elements or of the elements of the subgroups. The solution might contain additives like stabilizers, complex builders, pigments and beating additives.
WO 2008/098157 relates to a colouring solution for dental ceramic framework comprising a solvent, a colouring agent comprising metal ions, and a complexing agent, wherein the amount of complexing agent is sufficient to dissolve the colouring agent in the solvent.
WO 2009/014903 relates to a colouring solution for dental ceramic articles, the solution comprising a solvent and a colouring agent comprising rare earth element ions being present in the solution in an amount of at least about 0.05 mol/l solvent and transisition ions being present in the solution in an amount of about 0.00001 to about 0.05 mol/l solvent.
The present invention is intended to improve the known colouring solutions and to extend its use.